1. Field of the Invention
The present invention relates to an ocular depth dimension measurement apparatus which performs non-contact measurement of an ocular depth dimension.
2. Description of Related Art
As an apparatus for obtaining an ocular depth dimension, for example, there is known an apparatus which optically performs non-contact measurement of an axial length of an eye. As the apparatus, there is known an apparatus including an projection optical system arranged to project low coherent light onto an eye, an interference optical system arranged to obtain (detect) an interference signal by synthesizing and making the light reflected from a fundus and the light reflected from a cornea interfere with each other, and an optical path length changing member, which obtains the axial length based on the obtained interference signal and the position of the optical path length changing member (see Japanese Patent Application Unexamined Publication Hei02-297332).
However, the above-described apparatus has a problem that the obtained interference signal has a low S/N ratio since the light reflected from the cornea having a high reflectance and the light reflected from the fundus having a low reflectance are made to interfere with each other, so that measurement error is increased. In order to increase the S/N ratio of the interference signal, it is necessary to project strong light onto the eye, which becomes a burden on the eye.